Blender performance is the subject of considerable engineering by blender manufacturers. Efforts to improve blend consistency and efficiency have been directed to areas including blender cutter speed, blender cutter shape, and blender jar sidewall geometry. While each is effective in improving performance in certain instances, these efforts also have their limitations.
Blender cutter speed and speed variation has often been used to improve blending processes by speeding up or making variable the cutting and blending action of the cutter assembly. However, if the blades move too fast, then the rapid rotation may cause cavitation. If a user must manually vary the speed of operation of the blender, then such manual work requires user attention during some or all of the blending process.
Blender cutter assemblies have also been engineered to help move material being processed as well as improve the processing of the material. The pitching of the blade may promote some vertical movement of material being processed. Angling of the blade will change the blade path. If blade shape (including pitch and angle) is too aggressive, however, then the design may put extra strain on the blender motor. If the blade shape is relatively flat, then it may be more prone to cavitation at high speeds of operation. In any event, the cutter assembly cannot alone be used to overcome dead zones that are created in the material in a jar as a result of the processing inside a particular jar geometry.
Jar sidewall geometry has also been used to try to improve blender performance. In the early 1980's, for instance, a Nutone® blender (manufactured by Scovill) included a generally triangular-shaped jar. Two of the walls of the Nutone blender jar included bumps. The third wall had no bump. Further, the triangular cross-section of the blender was not symmetrical as the third wall was longer than the first two walls. The cutter assembly was set closer to the third wall (no bump) than the other two walls. In operation, presumably as a result of the asymmetric sidewall geometry, the blender formed a vortex in the material being processed with the vortex centered away from the axis defined by the shaft carrying the cutter. This movement of the vortex is expected to help the efficiency of that blender.
Another recent attempt to improve blender operation through sidewall modification is described in published U.S. Patent Application No. US2003/0213373 owned by K-Tec. As with the Nutone blender, this blender manufactured by K-Tec claims to improve the performance of the blender by making the sidewalls asymmetrically configured around the central axis of the cutter assembly. In the K-Tec blender, a fifth wall is truncated so that it is closer to the blade path of the cutter assembly. As explained in that patent application, this geometry moves the vortex of blended material in the blender away from the central axis and therefore improves performance of the blender.
As seen in both the Nutone and K-Tec blender jar configurations, the manipulation of sidewall geometry to an asymmetric configuration affects the horizontal flow of material within the blender jar. However, the sidewall geometry only primarily affects the horizontal flow of material. That is, the movement of material in the cross-sectional planes perpendicular to the vertical axis of the blender jar is affected. Therefore, the sidewall geometry is limited to essentially affecting only two dimensional change in material flow, i.e., in a single plane.